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Re: strange vibration and EGT readings at small RPM range.
by Roger Lee » 6 years ago
The higher the rpm at mag check the higher the mag drop. With a mag check at 3500 - 4000 rpm on the ground normal rpm loss is usually about 50 - 100 (occasionally 120). These numbers will depend on if you use an analog gauge (harder to read) vs a digital which reads in tens (easier to read). Your 50 is normal.
Vibration many times comes from prop blades out of track, prop needs a dynamic balance, carbs not in sync at higher rpms, but okay at lower rpms.
Spark plugs could also be a contributor.
Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell
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Re: strange vibration and EGT readings at small RPM range.
by john kennedy » 6 years ago
Check the dog clutch in the gearbox, it has been the cause of vibration in a number of 912uls engines that I have been involved with. One way to prove this is to fly the aircraft and reduce power in level flight, then try reducing power with a nose high attitude, ie with a load still on the prop. It should only vibrate in level or nose down attitude.
Thank you said by: Robert Longmore
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Re: strange vibration and EGT readings at small RPM range.
by Robert Longmore » 6 years ago
ill try to gearbox check, as the rpm and engine are smooth at 4800 rpm and lower, as they should be..
i have changed spark plugs, all were as to be expected. i am considering changing the plug leads as to eliminate another possibility.
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Re: strange vibration and EGT readings at small RPM range.
by Roger Lee » 6 years ago
Have you weighed your floats?
Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell
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